The Shanghai Academy of Spaceflight Technology (SAST) is a Chinese space agency and subordinate of China Aerospace Science and Technology Corporation (CASC), it is referred to as The Eighth Academy of CASC. The agency was established in August 1961 as Shanghai Second Bureau of Electromechanical Industry, but was later renamed to Shanghai Academy of Spaceflight Technology in 1993.
Among various low-grade heat harvesting technologies, thermo-electrochemical cycle (TEC) exhibits superior thermoelectric conversion performance and allows for continuous thermoelectric conversion through flow reactors. Despite significant advancements in active materials, mechanism investigations on the mass transport and electrochemical reaction behaviors governing the critical charge/discharge processes in TEC remain limited, especially for the non-isothermal charge/discharge processes in TEC, which constrains further performance improvement. This study establishes a three-dimensional multi-physics coupling model to simulate the flow and mass transfer characteristics of active substances during the non-isothermal charge/discharge processes, analyzing the effects of channel dimensions, temperature, electrolyte flow rate, and current density on the distribution of active substances within porous electrodes. The results indicate that temperature differences during the charge/discharge processes lead to significant variations in the distribution of active materials within the flow reactor, which further guides the design and selection of reactor flow channels at different temperatures. Under optimal flow channel design and operating conditions, TEC exhibits a maximum power density of 1.44 W/ m2 and a maximum relative Carnot efficiency of 10.2 % when the charging and discharging temperatures are 40 degrees C and 10 degrees C, respectively. This study is anticipated to provide novel insights for the optimization and design of electrochemical reactors for TEC.
Molybdenum disulfide MoS2 is an attractive solid lubricant because weak interlayer interactions enable easy shear, yet its wear resistance deteriorates at low temperatures. Ti doping serves as a microstructural design strategy to strengthen MoS2 for cryogenic service. Experiments and simulations show that dispersed Ti modifies local bonding, induces Ti-S coordinated configurations, and builds an interlayer network of Ti, S, and Ti-S clusters. This nanoscale architecture raises hardness to 1.93GPa and elastic modulus to 45.30GPa through lattice distortion and strong pinning that hinder interlayer shear. Although the strengthened interface increases the friction coefficient, it markedly lowers wear at 223K. Atomistic simulations reveal a transition from progressive interlayer sliding and local delamination in pristine MoS2 to coherent block-like deformation of pinned layers, which promotes more uniform stress accommodation. The associated increase in bending stiffness also suppresses wrinkling, offering a clear design route for durable solid-lubricant coatings in low-temperature environments.
This paper develops a systematic phased proximity rendezvous control strategy based on differential correction algorithm using impulsive thrust around cislunar libration points. The rendezvous scenario discussed consists of far-range guidance (relative distance within 100 km) and close-range approach (relative distance within 500 m). Alongside the booming of near-Earth spaceflight, the rendezvous technique is being matured with the associated orbital control algorithm studied thoroughly by both engineering field and academia in the framework of C-W or T-H equation. In the new era of lunar exploration, the libration point L1 and distance retrograde orbit (DRO) is a significant potential transition station for cislunar exploration yet critical parameters are lacking in systematical discussion. In particular, in the rendezvous scenario, the relative orbital control in the framework of circular restricted three-body problem (CR3BP) is being an open question: if its effectiveness is validated for both L1 and DRO; if it can be extended to multi-objective optimization as an engineering compensation between fuel consumption and guidance time; how its performances like the field-of-view angle and final deviation look like; if the control scheme is applicable to phasing with relative distance remarkably larger than the one of far-range; how sensitive it is to the uncertainties. This paper is devoted to the addressment of the aforementioned questions.
Dental restorations feature intricate surface contours, necessitating an effective path planning strategy of grinding tools to achieve precise outcomes. A novel tool path generation strategy based on offset surfaces was proposed for grinding of complex ceramic denture crowns. This strategy employed a half-edge data structure to reconstruct the topology of the triangular mesh model and leveraged the topological relationships among facets to develop a division algorithm specifically for denture crowns. Based on the structural characteristics of denture crowns and machine tool performance, these crowns were categorized into four areas. The vertex offset method was utilized to create offset surfaces for grids in each area, while the iso-planar method calculated the initial tool path corresponding to these offset surfaces. Optimization algorithms were introduced to rectify issues such as redundancy in tool paths, self-intersections, Z-shaped trajectories, overcutting in ridge regions, and the need for special optimization in cavity regions present in the original tool path. Given that the offset surface mesh derives from an original model mesh through an offset process, its density correlates with feature complexity; this property enables fewer tool points while still meeting accuracy requirements. Furthermore, these optimization algorithms effectively addressed defects found in initial paths and facilitated efficient high-precision grinding of denture crowns. Experimental results indicated that surface accuracy and machining efficiency achieved by this algorithm meet medical standards.
This article addresses the prescribed-time tracking control problem for spacecraft proximity operations under spatial motion constraints, including collision avoidance and visibility maintenance. To prevent collisions with target appendages and obstacles, a cardioid-shaped keep-out zone is established around the target, forming a safety corridor, while a capsule-shaped envelope is defined for the chaser spacecraft to facilitate the analytical computation of collision distances. In addition, a conical visibility region is constructed to ensure persistent observation of target features, which transforms visibility maintenance into an equivalent collision avoidance formulation. Subsequently, a prescribed-time safe proximity controller is developed by employing artificial potential fields and a robust integral of the sign of the error-based disturbance observer in conjunction with the time-scale transformation technique. Lyapunov stability analysis shows that the designed controller guarantees that the chaser reaches the desired position within a prescribed finite time, while strictly complying with spatial motion constraints, despite the presence of disturbances. Finally, the efficacy of the proposed method is validated through comprehensive numerical simulations.
